Ok so I really like this Xterra and the price is right. But it makes a weird sound at the front of the engine. All the forums say its a timing chain problem which doesnt really scare all that much. I'm capable of chaniging it. Bit I will make the dealer do it or I just wont buy it.

Also make a driveline vibration (i think) around 75 MPH.
So can I get another 120000 miles out of this truck?

Weird sound in the front huh? Unfortunately weird sound could mean a lot of things, but seeing as you haven't yet bought the vehicle, I'd definitely make getting that fixed a condition prior to buying. I kind of doubt a noise that sounds like the timing chain would be a SMOD, but it's best to make sure the dealership covers any kind of cost associated with keeping it drivable without passing it off to you. Be sure they don't try tacking up the price of the vehicle just because they fixed something, they're supposed to sell a good product at the price they already agreed to.

Idling rough at a stop is usually a sign that a tuneup is needed. Vibration at high speed could be the alignment. The noise is still weird, what kind of noise is it? Like rapid squeaks, or a low drone, or a high pitched squeal, or something mechanical sounding?

it sounds a-lot like the buick did when one of the idler pulleys went bad. I put it up on ramps today the driveline looks pristine. It being 4x4 i thought I would find mud hidden somewhere but no such luck.

That is the timing chain guides you are hearing. They will need to be changed. It's a very involved job (read over $1000). Driveline vibration is most likely a U-joint at that age. There are two on the front driveshaft and one on the rear driveshaft.

OK so I pulled the trigger because they wanted to get rid of it. Basically I got it below wholesale. Then I was sitting with the finance guy and he said I can buy a warranty to 100k for 2k so I fifgured well it will cost me a $500 in parts just to fix it. I might as well. Plus work pays for the car anyways.

Driving it I must say I really like it. Somebody smoked in it so I will be cleaning it thouroughly.

I got my X the same way too, dealership needed it gone and was willing to make a deal. Took me a while to get the maintenance caught up on it, so figure in that it will take at least $1k over the next 4-5 months before everything is really the way it should be. But after that things should get nice.

Good luck and have plenty of fun with the newest addition to your family